Failure behaviour of fatigue-tested post and cores

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Mechanical Engineering

Background:

• Evaluating long-term dental restoration performance in clinical trials is lengthy.
• Mechanical fatigue testing offers a potential alternative to clinical trials for assessing restoration durability.
• Understanding failure modes under cyclic loading is critical for improving dental restorative materials.

Purpose of the Study:

• To investigate the failure mechanisms of post and core restored teeth under cyclic mechanical loading.
• To compare the fatigue failure behavior with quasistatic failure modes.
• To determine the influence of core material (amalgam vs. composite) on failure characteristics.

Main Methods:

• Eighty-seven premolar teeth were restored with titanium alloy posts and amalgam or composite cores.
• Specimens underwent cyclic loading at 45 degrees to the long axis at 50-70% of mean quasistatic failure loads (5 Hz frequency).
• Teeth were categorized into short (<10^4), intermediate (10^4-10^5), and long (>10^5) cycle survival groups.

Main Results:

• Failure behavior changed significantly after approximately 10^5 cycles for both amalgam and composite cores, most notably in the composite group.
• Catastrophic failures included core fracture in the amalgam group and post fracture in the composite long-survival group.
• Three post fractures occurred at locations susceptible to fatigue failure.

Conclusions:

• Fatigue failure characteristics of post and core restorations differ significantly from quasistatic failure.
• Fatigue testing, particularly beyond 10^5 cycles, is essential alongside quasistatic tests for comprehensive evaluation.
• Results highlight the need for fatigue-resistant materials and designs in post and core restorations.